This disclosure relates to diesel engines, and, more particularly, to a system and process for detecting conditions indicative of substandard performance of the cylinders within a large scale multi-cylinder diesel engine.
Diesel engines are internal combustion devices in which high compression ratios produce auto ignition of an air/fuel mixture. In such devices, because the air/fuel mixture is ignited under a compressive force, conventional ignition processes (e.g., those utilizing spark ignition, such as that found in an Otto cycle engine) are inapplicable. Thus, fewer options for influencing the combustion method are available. Control of the engines are attained primarily through the influence of a fuel injection process and the amount of fuel injected. Differences in tolerances of the components of an engine oftentimes result in variation in the behavior of each of the individual cylinders of the engine. This variation causes less than optimum performance to be realized by the engine. Such performance is characterized by low power output as a result of weak cylinders. Operation of the engine on a weak cylinder generally results in increased fuel consumption, emission of harmful substances, vibration, excessive noise, and shortened service life.
While increased fuel consumption, emission of harmful substances, vibration, excessive noise, and shortened service life are generally indicative of a weak cylinder condition, such indicators require lengthy periods of monitoring of a large number of attributes of the engine. Direct methods of weak cylinder detection have been performed by highly skilled artisans using solely their experience-trained senses. Such methods are more characteristic of art forms than of technical diagnostic processes. In these methods, an operator of a diesel engine brings the engine up to a load and a speed and allows the engine to reach a steady state condition. Thereafter, the operator adjusts the fuel volume flowing from one of the fuel pumps to one of the cylinders. For each cylinder, the skilled operator listens to the sound emanating from the cylinder and makes a determination regarding the response of the cylinder to the changed volume of fuel being supplied. Given even a narrow range of environmental and other conditions, such a determination is generally highly subjective and open to various interpretations even by the same operator. Based on the determination itself, the operator makes a judgment as to the condition of the components of each cylinder and thereby recommends remedial or other action.
While such methods have been effective for many years, they are not the most economical, effective, or accurate means of determining the condition of diesel engines. Furthermore, they are certainly not the most time-efficient methods or a means that can be carried out with the frequency required by the operation of large scale equipment into which the diesel engine is incorporated.
A method and system for overcoming the drawbacks associated with the detection of conditions indicative of substandard performance of the cylinders in a diesel engine is described herein. The system provides for diagnostic monitoring of the cylinders of the engine by monitoring the system response to the selective temporary arrest of each cylinder as the engine is maintained at a constant load and speed. The method includes making a comparison of the average fuel required per cylinder of the engine operating under the power of all cylinders and a subsequent average fuel requirement for each cylinder of the engine operating under the successive arrest of each of the cylinders or a group of cylinders (at a selected engine speed and load). The process is repeated until each cylinder is individually (or collectively) removed and operationally restored and all of the data can be compiled and considered in order to statistically rank the performance of each cylinder, thereby allowing recommendations to be made concerning corrective measures regarding cylinders that are not performing up to predetermined standards.
The system includes an engine control unit disposed in operable communication with the engine and a computer disposed in informational communication with the engine control unit. The engine control unit is in operable communication with the engine through a communication element that includes a valve. The communication element may be a wiring harness. The informational communication with the engine control unit includes a dynamic signal, which controls the amount of fuel being dispensed to each cylinder, and a feedback signal, which provides a quantitative value representative of the amount of fuel being dispensed to each cylinder. The system takes into account speed and load and measures the amount of time over which fuel is dispensed to the cylinder. The time value is compared to an associated value in a linearization or lookup table, thereby allowing a determination to be made regarding the amount of fuel required by the cylinder to maintain the speed and load. Such a determination allows a recommendation to be made with respect to desirable, remedial, or modification measures that should be undertaken with respect to the cylinder.